Study on Reactive Power and Harmonic Characteristics of DC Ice-melting Technology based on RTDS Simulation and Field Test
TELKOMNIKA, Vol.14, No.3A, September 2016, pp. 1~8
ISSN: 1693-6930, accredited A by DIKTI, Decree No: 58/DIKTI/Kep/2013
DOI: 10.12928/TELKOMNIKA.v14i3A.3117
1
Study on Reactive Power and Harmonic Characteristics
of DC Ice-melting Technology based on RTDS
Simulation and Field Test
1
2
Lin Xu1, Yang Han*2
State Grid Sichuan Electric Power Research Institute, No. 24, Qinghua Road, Chengdu, China
Department of Power Electronics, School of Mechatronics Engineering, University of Electronic Science
and Technology of China, Chengdu, China
*Corresponding author, e-mail: [email protected]
Abstract
To study the characteristics of reactive power and harmonic of 500kV DC de-icer, the ice-melting
technologies including the calculation method of critical ice-melting current, ice-melting time and maximum
ice-melting current are clarified. The detail ice-melting methods and strategies for the 500kV transmission
lines are proposed. Based on the ice-melting current calculation of Kang-Ding substation transmission
lines in Sichuan, China, the 500kV/150MVA DC de-icer is deployed for the 500kV transmission lines. The
effectiveness and feasibility of the ice-melting algorithm is validated by the RTDS simulation and the field
test results. It is proved that the harmonic distortions of voltage and current are increased with the
increasing ice melting current, which can be improved by the installation of passive filters.
Keywords: DC de-icer, Real time digital simulator (RTDS), ice-melting current, deicing operation mode,
harmonic and reactive power characteristics
Copyright © 2016 Universitas Ahmad Dahlan. All rights reserved.
1. Introduction
Icing disaster of AC and DC transmission lines in winter is one of the major natural
disasters in power system, which would cause the power supply interruption, even power
system splitting accident. The repair work is difficult and of long period. Therefore, the DC deicer is necessary for ice melting of AC and DC transmission lines [1-4].
From the existing literature, the dc-current ice-melting and over-current ice-melting
methods are two feasible means of de-ice melting schemes [5, 6]. By using the dc-current icemelting method, the required power capacity of power electronic converters can be greatly
reduced since the efficiency is not affected by the line reactance. The icing lines are perceived
as the load with dc power supply, which provides a short-circuit current with a lower voltage
rating. Two schemes can be adopted for heating of the icing wires, one adopts the power
rectifier at the generator side and another scheme adopts the converter at the network side.
Although the first approach reduces the investment, due to the limited capacity of the generator
and the large amount of power consumed by the icing lines, it is impractical for most of the
cases. Therefore, the dc ice-melting method based on the thyristor converter is the preferred
solution with a higher level of robustness, and the dc-voltage can be adjusted dynamically under
different circumstances [7-9].
This paper describes the principle of ice-melting method for the overhead lines, the
Kangding substations in Sichuan province, China, were studied and the ice-melting schemes for
several overhead transmission lines were designed. The detailed guidelines for parameters
design were implemented, which was based on the thyristor rectifiers and dc ice-melting device.
The presented scheme was implemented in real-time digital simulator (RTDS) platform, the
harmonic emission and reactive power consumption properties under different operation
conditions were analyzed. Finally, the aforementioned ice-melting scheme was practically
implemented, tested and the validity of the proposed scheme was validated by the field data,
which confirms the effectiveness of the methodology as well as the RTDS-based digital
simulation method.
Received June 8, 2016; Revised July 23, 2016; Accepted August 2, 2016
2
ISSN: 1693-6930
2. System Description of Ice-Melting
2.1. Selection of Ice Melting Current
In order to ensure effective ice-melting, the heat generated by the dc transmission line
conductors must be greater than the sum of the dissipated heat and the heat required for icemelting process. Therefore, the ice-melting currents of the dc transmission lines must be
determined first.
The heat generated by the ice-melting currents in the conductors is to increase the
conductor temperature to the melting point hence the icicles melt. A portion of the power loss
dissipates when the heat is transferred to the surface of conductors and another part of loss
dissipates across the surface, with the following analytical expression:
2
g
D
R
0.045
t
T0
0
t
I r2 R0Tr
Tr 10 g 0 db
RT 1 0.22
D
RT 0 RT 1
RT 0 RT 1
Ln
d
(1)
where Ir denotes the ice-melting current (A), R0 denotes the resistance of conductor at 0°C
(Ω/m), Tr denotes the ice-melting period (h), ∆t denotes the temperature difference between the
conductor and air (°C), g0 denotes the density of ice (g0=0.9 in case of glaze ice), b denotes ice
thickness, D denotes outer diameter of conductor with glaciation (cm), RT0 denotes the
equivalent thermal-conduction resistance of the ice layer (°C.cm/W), which is described as:
RT 0 Ln
D
273
d
(2)
where d denotes conductor diameter (cm), λ denotes thermal conductivity (W/°C.cm), λ=0.0227
in case of glaze, and λ=0.0012 in case of soft rime.
The parameter RT denotes the equivalent thermal resistance for convection and
radiation (°C.cm/W), in case of glaze, RT can be written as:
RT
1
0.09 D 0.22 0.73(VD)2 3
(3)
2.2. Selection of Ice Melting Mode
Under normal circumstances, the three-phase transmission lines at the AC-side are
shorted, by controlling the firing angle of the converter, the dc-side currents would result in icemelting effects for the ice across the three-phase transmission lines at the AC-side.
The two ice-melting circuit configurations are shown in Figure 1 and Figure 2,
respectively. Figure 1 shows the circuit diagram of the “I-I type” ice-melting system, where the
ice-melting period is T for the individual transmission line. Hence, the total time period for the
three transmission lines is 1.5T. Figure 1(a) shows the case of A-C mode, where the circuit
breakers WPQ11 and WNQ11 are closed for a period of 0.5T. Figure 1(b) and Figure 1(c) show
the case of B-C and A-B mode respectively.
The alternative approach using “I-II type” configuration is shown in Figure 2. Under this
scenario, the total time for ice-melting process is 2T. Figure 2(a) shows the case of AB-C mode,
where the circuit breakers WPQ11, WPQ12 and WNQ11 are closed for a period of 2T/3, and
the transmission lines for phase A and B are connected in parallel, and then connected in series
with phase C. Figure 2(b) shows the case of AC-A mode.
Notably, the total line resistance for the “I-II type” configuration is quite small, which
implies that the total active power consumption from the converter is also small. The total
capacity is reduced by 1/4 compared to the “I-I type” configuration. It can be concluded that the
“I-II type” configuration can be applied for ice-melting mode of long transmission lines.
TELKOMNIKA Vol. 14, No. 3A, September 2016 : 1 – 8
TELKOMNIKA
ISSN: 1693-6930
(a)
3
(c)
(b)
Figure 1. The “I-I type” ice-melting configurations: (a). A-C mode; (b). B-C mode; (c). A-B mode
(a)
(b)
Figure 2. The “I-II type” ice-melting configurations: (a). AB-C mode; (b). BC-A mode
2.3. Ice-Melting Scheme
The presented ice-melting device was installed at Kangding station, which is the hub for
the sending channel of the 500kV transmission lines for the Sichuan hydropower. Figure 3
shows the connection between Kangding station and its surrounding system, such as
Chongzhou, Danba, Gangudi, Hou ziyan station. These 500kV lines is connected at the two
poles on the DC-side of the ice-melting device by the I-I type or I-II type, shown as Figure 4,
where the ∆-∆-Y rectifier transformer is connected at the 35kV bus side, two 6-pluse rectifiers
are connected at the 10kV bus side of the transformer, separately.
Figure 3. The diagram of Kangding station and its surrounding system
Study on Reactive Power and Harmonic Characteristics of DC Ice-melting … (Yang Han)
4
ISSN: 1693-6930
idc
udc
i1abc
i35
i2abc
Figure 4. The schematic diagram of ice-melting device for transmission system
According to the Equation (1) and the parameter of the ice-melting line, the ice-melting
current idc, DC voltage Udc, active power P, reactive power Q and the firing angle θ are
calculated preliminarily shown in Table 1. It can be found that the ice-melting current and dc
voltage are different for the different types and lengths of 500kV lines. Once the input line
voltage of the rectifier is certain, the lower the DC output voltage is, the greater the firing angle
and required reactive power are.
Table 1. The calculation result of different 500kV lines
500kV line name
R(Ω/km)
L(km)
idc(A)
θ(°)
P(MW)
Q(MVar)
Udc(kV)
Kangding-gangudi
0.01158
32.5
5000
77.44
20.07
130.53
3.71
Kangding-chongzhou
0.01158
202.5
5000
19.67
117.32
63.55
23.45
Kangding-Chongzhou
0.01158
200
5000
21.16
115.82
66.07
23.16
Kangding-danba
0.01478
109
4500
52.01
65.02
99.41
14.56
Kangding-Hou ziyan
0.01808
50
4000
70.76
29.01
102.08
7.23
3. Implementation of Ice-Melting Controller on RTDS Platform
Figure 5 shows the physical interface system (including power amplifier) of ice-melting
controller with the RTDS simulation system. The RTDS simulation device provides the desired
voltage Udc, current idc and the 35kV bus voltage, and also provides the ice-melting controller
with the switching positions of the filter branches, the dc-side breaker. As shown in Figure 5, the
rectifier trigger signals as well as the opening/closing of each branch switching signals
generated by the ice-melting controller are sent back to the RTDS platform. Furthermore, the
controller acquires the voltage, current and switching position signals from the physical interface
box (including the power amplifier). After the execution of the complicated control algorithm, and
output trigger pulse signals and sub-closing signals of the ice-melting controller are sent back to
the RTDS platform. Following the last procedure, the closed-loop controller test of the icemelting device is realized in the advanced digital power system simulation RTDS platform.
In order to investigate the reactive power and harmonic characteristics of the controller
under different ice-melting currents, the experimental results are given based on the Kangdinggangudi line and I-I ice-melting type. Figure 6(a) shows the dynamic waveforms when the icemelting current is jumped from 4000A to 5000A at time t=0.2s.Figure 6(b) shows the steadystate waveforms when the ice-melting current is 5000A. From top to bottom, the signals are as
the following: (1) Firing pulse gy1~gy6 and gd1~gd6. (2) The reference and measured dc
current idcref, idc. (3) 500kV current IL1A~IL1C. (4) 220kV current IL2A~IL2C. (5) 35kV current IL3A~IL3C.
(6) 500kV voltage N1~N3. (7)220kV voltage N4~N6. (8) 35kV voltage N7~N9. Table 2 shows
the firing angle θ, the active power P, the reactive power Q, dc-side voltage Udc, the THD of
TELKOMNIKA Vol. 14, No. 3A, September 2016 : 1 – 8
TELKOMNIKA
ISSN: 1693-6930
5
500kV/220 kV/35kV voltage and the 11th, 13th harmonic components under different ice-melting
current conditions.
Figure 5. The closed-loop test system of the De-icer controller and the RTDS platform
As shown in Figure 6, the De-icer can keep at the reference ice-melting current, when
the reference is changed, the dc-side current has a small fluctuation and reaches to the given
value soon, the steady error is nearly zero. According to the limit of IEEE 519-1992 standard for
the harmonic injection to the utility grid, the THD for 35kV voltage should be less than 3.0%, and
the THD for 220 kV and 500kV voltage should be less than 2.0%. Due to the short circuit
capacity of the station is 2062MVA, and then the limitations of 11th and 13th harmonic current
imposed by the IEEE standard are 46.2A and 38.8A, respectively.
(a)
(b)
Figure 6. The RTDS simulation results: (a) the dynamic waveforms when the ice-melting current
changed from 4000A to 5000A. (b)The steady-state waveform when the current is 5000A
Study on Reactive Power and Harmonic Characteristics of DC Ice-melting … (Yang Han)
6
ISSN: 1693-6930
Table 2. Comparison under different ice-melting currents
Parameter
θ (deg)
Udc (kV)
P(MW)
Q(MVar)
500kV voltage THD (%)
220kV voltage THD (%)
35kV voltage THD (%)
th
35kV 11 current(A)
th
35kV 13 current (A)
500A
89.01
0.33
0.41
16.01
0.095
0.24
0.89
25.67
13.34
1000A
87.74
0.7
0.97
29.5
0.22
0.55
2.1
46.85
31.13
Ice-melting current
2000A
3000A
85.27
82.71
1.46
2.21
3.32
7.29
55.95
81.67
0.44
0.63
1.11
1.59
4.24
6.17
87.9
127.67
66.02
98.16
4000A
80.09
2.96
12.62
106.76
0.79
2
7.77
162.92
128.68
5000A
77.44
3.71
20.07
130.53
0.9
2.28
8.95
195.66
153.59
4. Field Result
The proposed 150MVA DC de-icer was implemented in the 500kV Kangding station, as
shown in Figure 7. Due to the similarity of the field results, Figure 8 shows the test results when
the ice-melting current are 1000A and 5000A using I-I type ice-melting mode, respectively. We
can see that the distortion of voltage and current in each side of the transformer increased
significantly when the ice-melting current changes from 1000A to 5000A. Meanwhile, Figure 9
shows the test trend of 11th and 13th harmonic component and ratio with the varying icemelting current. During the time [0, 130min], the ice-melting current increased from 0A to 5000A
with the step increase of 1000A, the 11th harmonic voltage distortion rate increases from 0.2%
to 5.7%, the 11th harmonic current component increases from 0A to 190A, the 13th harmonic
voltage distortion rate increases from 0.2% to 6.3%, the 13th harmonic current component
increases from 0A to 148A. And then, during the time [130min, 170min], the current reduced
from 5000A to 0A. It can be found that the field result is consistent with the RTDS simulation
result, which verifies the validity of the proposed DC de-icer techniques.
(a)
(b)
Figure 7. (a) Valve hall, (b) Installation of DC ice-melting device in the substation
TELKOMNIKA Vol. 14, No. 3A, September 2016 : 1 – 8
TELKOMNIKA
ISSN: 1693-6930
(a)
7
(b)
Figure 8. The voltage and current waveforms at each side of the 500kV transformer. (a) I-I type
ice-melting mode, idc=1000A), (b) (I-I type ice-melting mode, idc=5000A)
(a)
(b)
Figure 9. The test trends of harmonic current and voltage with the varying ice-melting current.
(a) the 11th and 13th harmonic current of the 35kV line, (b) the 11th and 13th voltage distortion
rate of the 35kV line.
5. Conclusion
According to the actual application of dc de-icing technology at 500kV Kangding station,
it can be concluded that timely applied de-icing play an essential role in protecting transmission
lines and towers from damage, lowering line trips, and ensuring system safety.
To study the characteristics of reactive power and harmonic of DC de-icer, the
deployment principle of dc de-icers in a grid and an optimized de-icing dispatch strategy taking
into account more constraints has been initiated. The RTDS simulation model of 500kV
Kangding station with 180MVA DC de-icer model and dc de-icing technology is introduced in
detail. With this model, the characteristics of reactive power and harmonic at the Kangding
station are analyzed. Also the application of DC de-icer in Kangding station is also given, which
shows that DC de-icer is an effective means to tackle the ice disaster for transmission lines.
References
[1]
Chang Hao, Shi Yan, Yin Wei-yang, Zhang Min. Ice-Melting Technologies for HVAC and HVDC
Transmission Line. Power system technology. 2008; 32(5): 1-6.
Study on Reactive Power and Harmonic Characteristics of DC Ice-melting … (Yang Han)
8
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
ISSN: 1693-6930
Jiang Xingliang, Ma Jun, Wang Shaohua, et.al. Transmission lines ice accidents and analysis of the
formative factors. Electric Power. 2005; 38(11): 27-30.
Wu Wenhui. Causes and precaution measure for tripping trouble of transmission line covered with
ice. High Voltage Engineering. 2006; 32(2): 110-112.
Yuan Jihe, Jiang Xingliang, Yi Hui, et.al. The present study on conductor icing of transmission lines.
High Voltage Engineering. 2003; 30(1):6-10.
Huneault M, Langheit C, S-Arnaud R, et.al. A dynamic programming methodology to develop icemelting strategies during ice storms by channeling load currents in transmission networks. IEEE
Transaction on Power Delivery. 2005; 20(2): 1604-1610.
Horwill C, Davidson C C, Granger M. An application of HVDC to the ice-melting of transmission lines.
Proceedings of the 2005/2006 IEEE PES Transmission and Distribution Conference and Exhibition,
Dallas, TX, USA. 2006: 529-534.
Xie Huifan. Modeling of Gao-Zhao HVDC with deicing function based on EMTDC. Proceedings of
the Asia-Pacific Power and Energy Engineering Conference, Wuhan, China. 2011: 1-4.
Xie Huifan, Wang Haijun, Chen Qian. Analysis on reactive power and harmonics of Gao-Zhao HVDC
under deicing operation mode. Automation of Electric power systems. 2011; 35(19): 77-84.
Xu Shukai, Yang Yu, Fu Chuang. Simulation Study of DC Ice-melting Scheme for China Southern
Power Grid. Southern Power System Technology. 2008; 2(2): 31−36.
TELKOMNIKA Vol. 14, No. 3A, September 2016 : 1 – 8
ISSN: 1693-6930, accredited A by DIKTI, Decree No: 58/DIKTI/Kep/2013
DOI: 10.12928/TELKOMNIKA.v14i3A.3117
1
Study on Reactive Power and Harmonic Characteristics
of DC Ice-melting Technology based on RTDS
Simulation and Field Test
1
2
Lin Xu1, Yang Han*2
State Grid Sichuan Electric Power Research Institute, No. 24, Qinghua Road, Chengdu, China
Department of Power Electronics, School of Mechatronics Engineering, University of Electronic Science
and Technology of China, Chengdu, China
*Corresponding author, e-mail: [email protected]
Abstract
To study the characteristics of reactive power and harmonic of 500kV DC de-icer, the ice-melting
technologies including the calculation method of critical ice-melting current, ice-melting time and maximum
ice-melting current are clarified. The detail ice-melting methods and strategies for the 500kV transmission
lines are proposed. Based on the ice-melting current calculation of Kang-Ding substation transmission
lines in Sichuan, China, the 500kV/150MVA DC de-icer is deployed for the 500kV transmission lines. The
effectiveness and feasibility of the ice-melting algorithm is validated by the RTDS simulation and the field
test results. It is proved that the harmonic distortions of voltage and current are increased with the
increasing ice melting current, which can be improved by the installation of passive filters.
Keywords: DC de-icer, Real time digital simulator (RTDS), ice-melting current, deicing operation mode,
harmonic and reactive power characteristics
Copyright © 2016 Universitas Ahmad Dahlan. All rights reserved.
1. Introduction
Icing disaster of AC and DC transmission lines in winter is one of the major natural
disasters in power system, which would cause the power supply interruption, even power
system splitting accident. The repair work is difficult and of long period. Therefore, the DC deicer is necessary for ice melting of AC and DC transmission lines [1-4].
From the existing literature, the dc-current ice-melting and over-current ice-melting
methods are two feasible means of de-ice melting schemes [5, 6]. By using the dc-current icemelting method, the required power capacity of power electronic converters can be greatly
reduced since the efficiency is not affected by the line reactance. The icing lines are perceived
as the load with dc power supply, which provides a short-circuit current with a lower voltage
rating. Two schemes can be adopted for heating of the icing wires, one adopts the power
rectifier at the generator side and another scheme adopts the converter at the network side.
Although the first approach reduces the investment, due to the limited capacity of the generator
and the large amount of power consumed by the icing lines, it is impractical for most of the
cases. Therefore, the dc ice-melting method based on the thyristor converter is the preferred
solution with a higher level of robustness, and the dc-voltage can be adjusted dynamically under
different circumstances [7-9].
This paper describes the principle of ice-melting method for the overhead lines, the
Kangding substations in Sichuan province, China, were studied and the ice-melting schemes for
several overhead transmission lines were designed. The detailed guidelines for parameters
design were implemented, which was based on the thyristor rectifiers and dc ice-melting device.
The presented scheme was implemented in real-time digital simulator (RTDS) platform, the
harmonic emission and reactive power consumption properties under different operation
conditions were analyzed. Finally, the aforementioned ice-melting scheme was practically
implemented, tested and the validity of the proposed scheme was validated by the field data,
which confirms the effectiveness of the methodology as well as the RTDS-based digital
simulation method.
Received June 8, 2016; Revised July 23, 2016; Accepted August 2, 2016
2
ISSN: 1693-6930
2. System Description of Ice-Melting
2.1. Selection of Ice Melting Current
In order to ensure effective ice-melting, the heat generated by the dc transmission line
conductors must be greater than the sum of the dissipated heat and the heat required for icemelting process. Therefore, the ice-melting currents of the dc transmission lines must be
determined first.
The heat generated by the ice-melting currents in the conductors is to increase the
conductor temperature to the melting point hence the icicles melt. A portion of the power loss
dissipates when the heat is transferred to the surface of conductors and another part of loss
dissipates across the surface, with the following analytical expression:
2
g
D
R
0.045
t
T0
0
t
I r2 R0Tr
Tr 10 g 0 db
RT 1 0.22
D
RT 0 RT 1
RT 0 RT 1
Ln
d
(1)
where Ir denotes the ice-melting current (A), R0 denotes the resistance of conductor at 0°C
(Ω/m), Tr denotes the ice-melting period (h), ∆t denotes the temperature difference between the
conductor and air (°C), g0 denotes the density of ice (g0=0.9 in case of glaze ice), b denotes ice
thickness, D denotes outer diameter of conductor with glaciation (cm), RT0 denotes the
equivalent thermal-conduction resistance of the ice layer (°C.cm/W), which is described as:
RT 0 Ln
D
273
d
(2)
where d denotes conductor diameter (cm), λ denotes thermal conductivity (W/°C.cm), λ=0.0227
in case of glaze, and λ=0.0012 in case of soft rime.
The parameter RT denotes the equivalent thermal resistance for convection and
radiation (°C.cm/W), in case of glaze, RT can be written as:
RT
1
0.09 D 0.22 0.73(VD)2 3
(3)
2.2. Selection of Ice Melting Mode
Under normal circumstances, the three-phase transmission lines at the AC-side are
shorted, by controlling the firing angle of the converter, the dc-side currents would result in icemelting effects for the ice across the three-phase transmission lines at the AC-side.
The two ice-melting circuit configurations are shown in Figure 1 and Figure 2,
respectively. Figure 1 shows the circuit diagram of the “I-I type” ice-melting system, where the
ice-melting period is T for the individual transmission line. Hence, the total time period for the
three transmission lines is 1.5T. Figure 1(a) shows the case of A-C mode, where the circuit
breakers WPQ11 and WNQ11 are closed for a period of 0.5T. Figure 1(b) and Figure 1(c) show
the case of B-C and A-B mode respectively.
The alternative approach using “I-II type” configuration is shown in Figure 2. Under this
scenario, the total time for ice-melting process is 2T. Figure 2(a) shows the case of AB-C mode,
where the circuit breakers WPQ11, WPQ12 and WNQ11 are closed for a period of 2T/3, and
the transmission lines for phase A and B are connected in parallel, and then connected in series
with phase C. Figure 2(b) shows the case of AC-A mode.
Notably, the total line resistance for the “I-II type” configuration is quite small, which
implies that the total active power consumption from the converter is also small. The total
capacity is reduced by 1/4 compared to the “I-I type” configuration. It can be concluded that the
“I-II type” configuration can be applied for ice-melting mode of long transmission lines.
TELKOMNIKA Vol. 14, No. 3A, September 2016 : 1 – 8
TELKOMNIKA
ISSN: 1693-6930
(a)
3
(c)
(b)
Figure 1. The “I-I type” ice-melting configurations: (a). A-C mode; (b). B-C mode; (c). A-B mode
(a)
(b)
Figure 2. The “I-II type” ice-melting configurations: (a). AB-C mode; (b). BC-A mode
2.3. Ice-Melting Scheme
The presented ice-melting device was installed at Kangding station, which is the hub for
the sending channel of the 500kV transmission lines for the Sichuan hydropower. Figure 3
shows the connection between Kangding station and its surrounding system, such as
Chongzhou, Danba, Gangudi, Hou ziyan station. These 500kV lines is connected at the two
poles on the DC-side of the ice-melting device by the I-I type or I-II type, shown as Figure 4,
where the ∆-∆-Y rectifier transformer is connected at the 35kV bus side, two 6-pluse rectifiers
are connected at the 10kV bus side of the transformer, separately.
Figure 3. The diagram of Kangding station and its surrounding system
Study on Reactive Power and Harmonic Characteristics of DC Ice-melting … (Yang Han)
4
ISSN: 1693-6930
idc
udc
i1abc
i35
i2abc
Figure 4. The schematic diagram of ice-melting device for transmission system
According to the Equation (1) and the parameter of the ice-melting line, the ice-melting
current idc, DC voltage Udc, active power P, reactive power Q and the firing angle θ are
calculated preliminarily shown in Table 1. It can be found that the ice-melting current and dc
voltage are different for the different types and lengths of 500kV lines. Once the input line
voltage of the rectifier is certain, the lower the DC output voltage is, the greater the firing angle
and required reactive power are.
Table 1. The calculation result of different 500kV lines
500kV line name
R(Ω/km)
L(km)
idc(A)
θ(°)
P(MW)
Q(MVar)
Udc(kV)
Kangding-gangudi
0.01158
32.5
5000
77.44
20.07
130.53
3.71
Kangding-chongzhou
0.01158
202.5
5000
19.67
117.32
63.55
23.45
Kangding-Chongzhou
0.01158
200
5000
21.16
115.82
66.07
23.16
Kangding-danba
0.01478
109
4500
52.01
65.02
99.41
14.56
Kangding-Hou ziyan
0.01808
50
4000
70.76
29.01
102.08
7.23
3. Implementation of Ice-Melting Controller on RTDS Platform
Figure 5 shows the physical interface system (including power amplifier) of ice-melting
controller with the RTDS simulation system. The RTDS simulation device provides the desired
voltage Udc, current idc and the 35kV bus voltage, and also provides the ice-melting controller
with the switching positions of the filter branches, the dc-side breaker. As shown in Figure 5, the
rectifier trigger signals as well as the opening/closing of each branch switching signals
generated by the ice-melting controller are sent back to the RTDS platform. Furthermore, the
controller acquires the voltage, current and switching position signals from the physical interface
box (including the power amplifier). After the execution of the complicated control algorithm, and
output trigger pulse signals and sub-closing signals of the ice-melting controller are sent back to
the RTDS platform. Following the last procedure, the closed-loop controller test of the icemelting device is realized in the advanced digital power system simulation RTDS platform.
In order to investigate the reactive power and harmonic characteristics of the controller
under different ice-melting currents, the experimental results are given based on the Kangdinggangudi line and I-I ice-melting type. Figure 6(a) shows the dynamic waveforms when the icemelting current is jumped from 4000A to 5000A at time t=0.2s.Figure 6(b) shows the steadystate waveforms when the ice-melting current is 5000A. From top to bottom, the signals are as
the following: (1) Firing pulse gy1~gy6 and gd1~gd6. (2) The reference and measured dc
current idcref, idc. (3) 500kV current IL1A~IL1C. (4) 220kV current IL2A~IL2C. (5) 35kV current IL3A~IL3C.
(6) 500kV voltage N1~N3. (7)220kV voltage N4~N6. (8) 35kV voltage N7~N9. Table 2 shows
the firing angle θ, the active power P, the reactive power Q, dc-side voltage Udc, the THD of
TELKOMNIKA Vol. 14, No. 3A, September 2016 : 1 – 8
TELKOMNIKA
ISSN: 1693-6930
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500kV/220 kV/35kV voltage and the 11th, 13th harmonic components under different ice-melting
current conditions.
Figure 5. The closed-loop test system of the De-icer controller and the RTDS platform
As shown in Figure 6, the De-icer can keep at the reference ice-melting current, when
the reference is changed, the dc-side current has a small fluctuation and reaches to the given
value soon, the steady error is nearly zero. According to the limit of IEEE 519-1992 standard for
the harmonic injection to the utility grid, the THD for 35kV voltage should be less than 3.0%, and
the THD for 220 kV and 500kV voltage should be less than 2.0%. Due to the short circuit
capacity of the station is 2062MVA, and then the limitations of 11th and 13th harmonic current
imposed by the IEEE standard are 46.2A and 38.8A, respectively.
(a)
(b)
Figure 6. The RTDS simulation results: (a) the dynamic waveforms when the ice-melting current
changed from 4000A to 5000A. (b)The steady-state waveform when the current is 5000A
Study on Reactive Power and Harmonic Characteristics of DC Ice-melting … (Yang Han)
6
ISSN: 1693-6930
Table 2. Comparison under different ice-melting currents
Parameter
θ (deg)
Udc (kV)
P(MW)
Q(MVar)
500kV voltage THD (%)
220kV voltage THD (%)
35kV voltage THD (%)
th
35kV 11 current(A)
th
35kV 13 current (A)
500A
89.01
0.33
0.41
16.01
0.095
0.24
0.89
25.67
13.34
1000A
87.74
0.7
0.97
29.5
0.22
0.55
2.1
46.85
31.13
Ice-melting current
2000A
3000A
85.27
82.71
1.46
2.21
3.32
7.29
55.95
81.67
0.44
0.63
1.11
1.59
4.24
6.17
87.9
127.67
66.02
98.16
4000A
80.09
2.96
12.62
106.76
0.79
2
7.77
162.92
128.68
5000A
77.44
3.71
20.07
130.53
0.9
2.28
8.95
195.66
153.59
4. Field Result
The proposed 150MVA DC de-icer was implemented in the 500kV Kangding station, as
shown in Figure 7. Due to the similarity of the field results, Figure 8 shows the test results when
the ice-melting current are 1000A and 5000A using I-I type ice-melting mode, respectively. We
can see that the distortion of voltage and current in each side of the transformer increased
significantly when the ice-melting current changes from 1000A to 5000A. Meanwhile, Figure 9
shows the test trend of 11th and 13th harmonic component and ratio with the varying icemelting current. During the time [0, 130min], the ice-melting current increased from 0A to 5000A
with the step increase of 1000A, the 11th harmonic voltage distortion rate increases from 0.2%
to 5.7%, the 11th harmonic current component increases from 0A to 190A, the 13th harmonic
voltage distortion rate increases from 0.2% to 6.3%, the 13th harmonic current component
increases from 0A to 148A. And then, during the time [130min, 170min], the current reduced
from 5000A to 0A. It can be found that the field result is consistent with the RTDS simulation
result, which verifies the validity of the proposed DC de-icer techniques.
(a)
(b)
Figure 7. (a) Valve hall, (b) Installation of DC ice-melting device in the substation
TELKOMNIKA Vol. 14, No. 3A, September 2016 : 1 – 8
TELKOMNIKA
ISSN: 1693-6930
(a)
7
(b)
Figure 8. The voltage and current waveforms at each side of the 500kV transformer. (a) I-I type
ice-melting mode, idc=1000A), (b) (I-I type ice-melting mode, idc=5000A)
(a)
(b)
Figure 9. The test trends of harmonic current and voltage with the varying ice-melting current.
(a) the 11th and 13th harmonic current of the 35kV line, (b) the 11th and 13th voltage distortion
rate of the 35kV line.
5. Conclusion
According to the actual application of dc de-icing technology at 500kV Kangding station,
it can be concluded that timely applied de-icing play an essential role in protecting transmission
lines and towers from damage, lowering line trips, and ensuring system safety.
To study the characteristics of reactive power and harmonic of DC de-icer, the
deployment principle of dc de-icers in a grid and an optimized de-icing dispatch strategy taking
into account more constraints has been initiated. The RTDS simulation model of 500kV
Kangding station with 180MVA DC de-icer model and dc de-icing technology is introduced in
detail. With this model, the characteristics of reactive power and harmonic at the Kangding
station are analyzed. Also the application of DC de-icer in Kangding station is also given, which
shows that DC de-icer is an effective means to tackle the ice disaster for transmission lines.
References
[1]
Chang Hao, Shi Yan, Yin Wei-yang, Zhang Min. Ice-Melting Technologies for HVAC and HVDC
Transmission Line. Power system technology. 2008; 32(5): 1-6.
Study on Reactive Power and Harmonic Characteristics of DC Ice-melting … (Yang Han)
8
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
ISSN: 1693-6930
Jiang Xingliang, Ma Jun, Wang Shaohua, et.al. Transmission lines ice accidents and analysis of the
formative factors. Electric Power. 2005; 38(11): 27-30.
Wu Wenhui. Causes and precaution measure for tripping trouble of transmission line covered with
ice. High Voltage Engineering. 2006; 32(2): 110-112.
Yuan Jihe, Jiang Xingliang, Yi Hui, et.al. The present study on conductor icing of transmission lines.
High Voltage Engineering. 2003; 30(1):6-10.
Huneault M, Langheit C, S-Arnaud R, et.al. A dynamic programming methodology to develop icemelting strategies during ice storms by channeling load currents in transmission networks. IEEE
Transaction on Power Delivery. 2005; 20(2): 1604-1610.
Horwill C, Davidson C C, Granger M. An application of HVDC to the ice-melting of transmission lines.
Proceedings of the 2005/2006 IEEE PES Transmission and Distribution Conference and Exhibition,
Dallas, TX, USA. 2006: 529-534.
Xie Huifan. Modeling of Gao-Zhao HVDC with deicing function based on EMTDC. Proceedings of
the Asia-Pacific Power and Energy Engineering Conference, Wuhan, China. 2011: 1-4.
Xie Huifan, Wang Haijun, Chen Qian. Analysis on reactive power and harmonics of Gao-Zhao HVDC
under deicing operation mode. Automation of Electric power systems. 2011; 35(19): 77-84.
Xu Shukai, Yang Yu, Fu Chuang. Simulation Study of DC Ice-melting Scheme for China Southern
Power Grid. Southern Power System Technology. 2008; 2(2): 31−36.
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